<!DOCTYPE html>
<html>
<style>
#myCanvas {
  width: 100%;
  height: 100%;
  background-color: rgb(241, 241, 241);
}
</style>
<head>
  <link rel="stylesheet" type="text/css" href="canvas.css">
</head>
<body onload="load()">
<canvas id="myCanvas"></canvas>
<script>
function load() {
  var myCanvas = document.getElementById("myCanvas");
  myCanvas.setAttribute("width", 400);
  myCanvas.setAttribute("height", 400);
  var ctx = myCanvas.getContext("2d");
  ctx.clearRect(0, 0, 400, 400);
  ctx.fillStyle = "green";
  ctx.fillRect(0, 0, 200, 200);
}
</script>
</body>
</html>
